Laowa 90mm f2.8 2x macro

I’m on my second day as an official NLP licensee and have been working through issues. Up until this evening I have not been satisfied with my scans. I did some testing of this lens to get a better feel for it and thought perhaps others may be interested. I was curious about the diffraction limit (I’ve read conflicting things) and if there is focus shift when changing aperture as I like to focus at max aperture then stop down.

TLDR: f:8 is fine at 1:1 magnification. There is no focus shift.

My evaluation of different stops using this lens on a Leica SL (24MP Full Frame):

2.8: good
4: slightly better
5.6: indistinguishable from 4
8: seems like 2.8, but I could be imagining. If there is any diffraction it’s hard enough to detect that I consider this stop fine for negative scans.
11: definitely a slight bit of diffraction
16: obvious diffraction
22: unacceptable

For focus shift I put a ruler at an angle below my lens. I did not see any shift, however what surprised me is that the front range of focus stayed pretty static and the back range extended.

So with this understanding and taking the suggestion from some posts on this forum of “over” exposing I have had great success creating nice scans.

Here is my home made system:

Camera on manual, ISO100. Set light to 100%. Set the lens to 1:1, rough focus by shifting the whole assembly on the tube. I then fine focus using the macro rail (learning how to find a grainy place and focus on that was a trick). Stop the lens down to f8. Adjust shutter speed so that histogram is predomenently to the right, this shows on the camera as a 1 - 1.5 stop over exposure. Remote trigger.

With one 27 year old negative converted, my wife is totally happy with my lens purchase.

Very nice setup, is that a flash controller on the camera? That large focus wheel on the Novoflex Castel-M macro rail looks ideal.

Oh - and welcome to the community!

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…answering my own question but I guess that’s a (Godox?) flash controller that can also be used as a remote trigger.

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Correct. I used the flashes to illuminate the focus test. It is the Godox kit with the controller and two MF12 macro flashes.

The Novoflex rail is a really solid piece of kit. I’ve been playing around with macro and focus stacking and it works beautifully. For fine focus for film digitization it makes it easy to nail the focus.


Sorry for shameless plug but if you really wat to evaluate the lens and find the optimal settings which work the best for the whole frame, you may try Vlads Test Target , which was designed specifically for that task:


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That looks very useful!

It is indeed very useful, first of all for optimising your own setup, checking for uniform focus across the frame, establishing the optimum aperture, comparing different lenses and/or cameras. You will also find scattered across this and other forums (e.g. Digitizing Film with a Digital Camera and Negative Lab Pro Users forums on Facebook) that people have posted the results that they have achieved from a multitude of different lenses and cameras with this target which you can then compare with your own.

Your lens hasn’t been tested by Richard Karash here unfortunately but it’s a useful introduction: